(1917) Planting Of Irises by Bliss

The Planting of Irises. After considerable experimenting, it has been my practice for the last twelve years to transplant Irises so far as possible duriing the first week in August or thereabouts. Besides the unripeness of the rhizomes in June, I have been influenced by the supposition that at this time (immediately after the flowering) the embryo buds of the flower-spikes for the following season were being formed, as is the case with daffodils. These embryo buds are fully formed by September, and are visible to the naked eye, and do not appear to increase appreciably from then on to the end of the year. If this supposition is correct, since this period of embryo bud formation is. according to De Vries, one of extreme sensibilitv, it would largely account for the deficiency of the flower-spikes of the June-planted Irises in the experiment, and it would be of interest to make a further trial between March and August plantings. But even if the March-planted Irises should give more flower-spikes than August-planted, I think that August planting would still be preferable for the reasons Mr. Dykes gives, especially on account of the greater prevalence of adverse weather and soil conditions in March. My ground being open and exposed, March (or April) planted Irises have always suffered conspicuously, and have subsequently been more liable to disease. The drying off of the rhizomes when they are out of the ground for some time between taking up and replanting in August, though it causes loss of flower-spikes, appears to have a very good effect in checking the Iris disease. Out of the whole lot (900) replanted one year only one plant was found slightly attacked the following season. Though Irises are making roots throughout the season from spring on into autumn, it seems to me that they root intermittently rather than strictly continuously, being in this respect somewhat similar to Poeticus Narcissi. Whatever may be the case with the original species, with these garden hybrids it appears to depend chiefly on the weather. During dry weather there is, if not an actual resting period, a pause or slackening in root formation, and as August is the driest month (drier than either July or September), it would seem also for this reason the best time for replanting. Since the number of the flowering spikes in the following seasons has been chosen as a test of comparison, it will be useful to note that though the time the rhizomes are out of the ground, even when prolonged, does not injure the health of the plants in the least when they are transplanted in August, it has a very direct effect on the flowering in the following season. At one planting (about 600 plants), when the plants were about a week out of the ground', only about one-quarter to one-third flowered. Another year the plants (about 900) were from a fortnight to three weeks or more out of the ground, and only about a dozen flowered, though the plants were strong and exceptionally healthy. Last year I transplanted a dozen plants, replanting them immediately, and all flowered freely this year, some even more freelv than the duplicate plants left undisturbed. Since plants sent out by nurserymen must necessarily be out of the ground' some time, I think it would be of interest, if the experiment made at Wislev can be repeated comparing the results of March planting with early August (instead of June) plantings, to make it in duplicate, one lot of plants being replanted at once, and the other lot after an interval of a week or ten days. A. J. Bliss. (answer to article by Jenkins. The debate continues with Sturtevant, 1917

For more information on historic Irises visit the Historic Iris Preservation Society at